As if James Naughtie's 'Jeremy Hunt' slip-up wasn't enough, the BBC suffered another embarrassment today after a man interviewed on Radio 4's World at One who claimed to be a Liberal Democrat MP was revealed to be an imposter.

Presenter James Robbins's interview with ministerial aide Mike Crockart, in which he appeared to say he would be prepared to resign over the increase in tuition fees, turned out to be nothing of the sort.

The BBC blamed an incorrect number listed against his name in the corporation's directory of MPs' contact details.

All the "usual pre-broadcast questions" had been asked of the man over the phone, who had "maintained throughout that he was Mr Crockart and appeared credible", the corporation added.

But cursory knowledge of the Lib Dem MP for Edinburgh West might have revealed they had the wrong person. Crockart, the parliamentary private secretary to Scottish secretary Michael Moore, has a Scottish accent, while the BBC's interviewee – according to one listener – sounded like a "Yorkshireman putting on a squeaky voice".

A BBC spokeswoman said: "The World at One today broadcast an interview about tuition fees with a person wrongly believed to be Liberal Democrat MP Michael Crockart, a junior member of the government.

"The error came about after a call to an incorrect number listed in the BBC' s directory of MPs' contact details. The usual pre-broadcast questions were asked of the person concerned, who maintained throughout that he was Mr Crockart and appeared credible. Once the mistake was realised, steps were taken immediately to rectify the error and to ensure it was not repeated.

"A personal apology has been issued to Mr Crockart and a correction will be made on today's PM programme. We also apologise to our audiences for the error. The relevant part of the programme will be taken off iPlayer and other online platforms."

A fake Crockhart was also quoted in today's London Evening Standard, saying he would resign over the issue of tuition fees.

The quotes were picked up by the Press Association, which later issued a correction saying that the quotes attributed to the MP were from an impersonator.

The Lib Dem press office posted on Twitter: "For the record – Lib Dem PPS Mike Crockart was not on Radio 4 resigning earlier, it was an impersonator (he wasn't even Scottish)."

"We are absolutely clueless as to who it was," said a Lib Dem insider. "We figured it out when our head of media was talking to Mike on the phone and the fake Mike Crockart was on the World at One."

The BBC's most famous case of mistaken identity came four years ago when its 24-hour news channel interviewed a man who had been waiting in the BBC's reception, thinking he was computer expert Guy Kewney. Guy Goma gamely bluffed out the interviewer's questions on screen and briefly shot to fame as the "wrong guy".

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